Ambient temperature curing coating composition

ABSTRACT

Ambient temperature curing coating composition comprising a polysiloxane having the formula:  
                 
 
     wherein each R1 is selected from the group consisting of alkyl, aryl, and alkoxy groups having up to six carbon atoms, reactive glycidoxy groups, and OSi(OR3) 3  groups, wherein each R3 independently has the same meaning as R1, each R2 is selected from the group consisting of hydrogen and alkyl and aryl groups having up to six carbon atoms, and wherein n is selected so that the molecular weight of the polysiloxanes is in the range of from 500 to about 2,000, a glycidyl-functional acrylic polymer, and a hardener.  
     The composition can be used as a protective coating for large structures such as ships, bridges, buildings, industrial plants, or oil rigs.

[0001] This application claims priority of European Patent ApplicationNo. 00300192.2 filed on Jan. 12, 2000.

FIELD OF THE INVENTION

[0002] The present invention relates to a coating composition fastcuring at ambient temperature (touch dry in less than 2 hours at 25° C.)with a high solids content (>70% by weight) and a low VOC (<250 gramssolvent per liter of the composition, g/l) which can be used in durableprotective coatings.

BACKGROUND OF THE INVENTION

[0003] There has been increased concern in recent years about therelease of volatile solvents into the atmosphere, and there has been aconsequent need to reduce the volatile organic solvent content ofcoating, sealant, and adhesive compositions. This has not been easy forcoating compositions, which require a relatively low viscosity of below20 Poise for application by the usual methods of spray, roller or brush,and particularly not for coating compositions which have to be appliedand cure rapidly at ambient temperature, for example coatings for largestructures such as ships, bridges, buildings, industrial plants, and oilrigs.

[0004] Coating compositions generally need to contain a polymer toconfer film-forming properties, but any polymer used needs to be ofsufficient molecular weight to give the required low viscosity,particularly after pigmentation as a paint. Such low-viscosity polymersoften require long curing times to develop satisfactory mechanicalproperties, especially when cured at low temperature.

[0005] In WO 98/04594 a process is disclosed for the preparation of acurable polymer composition by polymerisation of a functionalolefinically unsaturated monomer in the presence of a reactive diluentwhich is a liquid organic compound of viscosity less than 2 Pa.s (20Poise) having at least one functional group which is substantiallynon-reactive with the functional olefinically unsaturated monomer andwhich is capable of reacting with a curing agent to form a polymernetwork. The major drawback of this technology is that this low-viscouscoating material results in a low final film T_(g) and moderatedurability.

[0006] In WO 96/16109 and WO 98/32792 an epoxy-polysiloxane coatingcomposition is disclosed that is prepared by combining water, apolysiloxane, a difunctional aminosilane hardener, optionally anorganooxysilane, and a non-aromatic epoxy resin. The maximum amount ofsolvent added to these compositions is approximately 420 g/l. Thecompositions are intended to be used as protective coatings for primedor galvanised steel, aluminium, concrete, and other substrates at a dryfilm thickness in the range of 25 μm to about two millimetres. Whilstthese compositions are employed as durable topcoats, their gloss andcolour retention properties when exposed to natural or accelerated testconditions (UV-A, UV-B) are not as expected for polysiloxane basedcompositions. This strongly affects the appearance of a coatedsubstrate.

[0007] U.S. Pat. No. 4,446,259 discloses a coating composition having aliquid carrier and a binder which is a blend of an olefinicallyunsaturated polymer containing glycidyl groups and a crosslinkablepolysiloxane having attached to the silicone atoms of its backbonealkyl, phenyl, and hydroxyl groups. These compositions are used asambient temperature curing protective coatings. The major drawback ofthese compositions is the presence of a relatively large amount oforganic solvent in the composition.

[0008] EP 0 822 240 discloses a coating resin composition comprising asilica-dispersed oligomer solution of an organosilane, an acrylic resin,and a curing catalyst. The coating resin compositions on average have asolid content in the range of 40-50% by weight. Consequently, thesecoating compositions have a VOC well above 250 g/l.

[0009] WO 97/22728 discloses a heat-resistant powder coating compositioncomprising at least one glycidyl-functional polyacrylic polymer and atleast one hydroxyl-functional polysiloxane. This composition is cured attemperatures greater than about 250° C. This high-curing temperaturerenders the composition unsuitable for use in the coating of largestructures such as ships, bridges, etc. Further, this coatingcomposition is not curable unless the coated surface is heated.

SUMMARY OF THE INVENTION

[0010] The present invention provides a solution to the drawbacksassociated with the above-mentioned prior art. The ambient temperaturecuring coating composition according to the present invention comprises:

[0011] a linear or branched polysiloxane having the formula

[0012] wherein each R1 is independently selected from the groupconsisting of alkyl, aryl, alkoxy groups having up to six carbon atoms,reactive glycidoxy groups, and OSi(OR3)₃ groups, wherein each R3independently has the same meaning as R1, each R2 is selected from thegroup consisting of hydrogen and alkyl and aryl groups having up to sixcarbon atoms, and wherein n is selected so that the molecular weight ofthe polysiloxanes is in the range of from 200 to about 5,000, preferably500-2,000,

[0013] a glycidyl-functional acrylic polymer, and

[0014] a hardener.

DETAILED DESCRIPTION OF THE INVENTION

[0015] It is preferred that R1 and R2 comprise groups having fewer thansix carbon atoms to facilitate rapid hydrolysis of the polysiloxane,which reaction is driven by the volatility of the alcohol analogueproduct of the hydrolysis. R1 and R2 groups having more than six carbonatoms tend to impair the hydrolysis of the polysiloxane due to therelatively low volatility of each alcohol analogue. Preference is givento the use of alkoxysilyl-functional polysiloxane. Methoxy-, ethoxy-,and silanol-functional polysiloxanes having molecular weights in therange of about 400 to about 2000 are preferred for formulating coatingcompositions according to present invention. Methoxy-, ethoxy-, andsilanol-functional polysiloxanes having molecular weights of less than400 would produce a coating composition that would be brittle and offerpoor impact resistance. Any liquid methoxy-, ethoxy-, andsilanol-functional polysiloxane with a molecular weight above 400 can beused, though it is preferred to use polysiloxanes with a molecularweight of less than 2000, as they enable the production of compositionsthat require few if any additional solvents to achieve applicationviscosity, i.e. which can be used without adding solvent in excess ofcurrent volatile organic content (VOC) requirements. In general, ahigh-molecular weight polysiloxane can be used without violating VOCrequirements by mixing it with a reactive or non-reactive diluent.However, normally this will affect film properties.

[0016] Suitable polysiloxanes that can be used in the compositionaccording to the present invention include: DC 3037 and DC 3074 (both exDow Corning), or SY 231, SY 550, and MSE 100 (all ex Wacker)

[0017] The glycidyl-functional acrylic polymer can be prepared bycopolymerizing one or more olefinically unsaturated monomers with aglycidyl-functional olefinically unsaturated monomer.

[0018] Examples of ethylenically unsaturated monomers which can becopolymerised with such a glycidyl-functional olefinically unsaturatedmonomer are acrylic esters such as butyl (meth)acrylate, methyl(meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-hexyl(meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate,2-ethylhexyl methacrylate or acrylate, cyclohexyl (meth)acrylate,2,2,5-trimethylcyclohexyl (meth)acrylate, isobornyl (meth)acrylate,acrylonitrile, methacrylonitrile, trimethoxysilyl propyl(meth)acrylate,and vinyl compounds such as styrene, vinyl acetate or vinyl chloride,wherein the notation (meth)acrylate means acrylate or methacrylate.

[0019] The glycidyl-functional olefinically unsaturated monomer ingeneral can be any one of the above-mentioned olefinically unsaturatedmonomers functionalised with one or more epoxide groups. Glycidylmethacrylate is one of the preferred monomers in the preparation of theglycidyl-functional acrylic polymer.

[0020] To prepare a coating composition with a low VOC, theglycidyl-functional acrylic polymer can be prepared, for example, byfree radical polymerisation or any other reaction in the presence of areactive diluent which is an organic compound of viscosity less than 2Pa.s (20 Poise) at 25° C. Preference is given to the use of a reactivediluent having at least one functional group which is substantiallynon-reactive with the olefinically unsaturated monomers and which iscapable of reacting with a curing agent to form a polymer network. Itwas found that low-viscosity polysiloxanes can be used in thepreparation of the glycidyl-functional acrylic polymer that is presentin the coating composition according to the present invention.

[0021] In a highly preferred embodiment, the reactive diluent is apolysiloxane, and this polysiloxane is the same as the polysiloxane thatis present in the coating composition according to the presentinvention.

[0022] Reactive diluents that can be used in the preparation of theglycidyl-functional acrylic polymer include alkoxysilyl-functionalpolysiloxanes, such as DC 3037 and DC 3074 (both ex Dow Corning), or SY231, SY 550, and MSE 100 (all ex Wacker), monomeric alkoxysilanes, suchas trimethoxypropyl silane and dimethoxydiphenyl silane, andorganofunctional monomeric alkoxysilanes, such as glycidoxypropyltrimethoxysilane, glycidoxypropyl triethoxysilane, acetoacetoxypropyltrimethoxysilane, and acetoacetoxypropyl triethoxysilane.

[0023] Very good results are achieved when the glycidyl-functionalacrylic polymer is obtained by polymerising a mixture comprisingglycidyl methacrylate and butyl acrylate in the polysiloxane that isalso present in the coating composition. Optionally, the mixture furthercomprises methyl methacrylate and/or other acrylic monomers. In general,it can be said that good results are achieved when the mixture comprises5-60% by weight of glycidyl methacrylate, 0-60% by weight of methylmethacrylate, and 10-80% by weight of butyl acrylate, better results areachieved when the mixture comprises 18-55% by weight of glycidylmethacrylate, 0-45% by weight of methyl methacrylate, and 25-70% byweight of butyl acrylate, and optimum results are achieved when themixture comprises 40-50% by weight of glycidyl methacrylate, 0-15% byweight of methyl methacrylate, and 50-60% by weight of butyl acrylate,wherein the % by weight is calculated based on the total amount ofolefinically unsaturated monomers present in the mixture before thestart of the polymerisation reaction.

[0024] As indicated above, preference is given to a process for thepreparation of the glycidyl-functional acrylic polymer fromethylenically unsaturated monomer by addition polymerisation while insolution. The polymerisation is preferably carried out in thesubstantial absence of non-functional volatile solvent, that is, asolvent which will not react with the curing agent for the polymer.

[0025] Alternatively, a small proportion, for example up to 10 to 20% byweight of the polymerisation reaction mixture, of a non-functionalvolatile solvent which is miscible with the reactive diluent can bepresent. Some or all of the monomers can be pre-dissolved in thereactive diluent, but preferably the monomers, together with (a) freeradical initiator(s) and any chain transfer agent used, are graduallyadded to the diluent. For example, the reactive diluent can be heated toa temperature in the range of 50-200° C., and the monomers, initiator,and chain transfer agent are added over a period of up to 12 hours,preferably in 4 hours, while the temperature of the solution ismaintained during the addition and for a further period of 0.5-4 hoursafter the addition. A further charge of initiator may be added duringthis further period to reduce the level of unreacted monomer. However,it is also possible to reduce this level by distilling off the unreactedmonomer from the reaction mixture.

[0026] The free radical initiator can for example be a peroxide orperoxy-ester such as benzoyl peroxide, di-tert-butyl peroxide,tert-butyl peroxy-3,5,5-trimethylhexanoate,2,5-bis(2-ethylhaxanoyl-peroxy)-2,5-dimethylhexane, or tertiary butylperoctoate or an azo compound such as azobisisobutyronitrile orazo-bis(2-methylbutyronitrile).

[0027] A chain transfer agent, for example dodecanethiol, butanethiol,pentaerythritol tetra (mercaptopropionate), mercaptopropyltrimethoxysilane, or dibutyl phosphite, may be present duringpolymerisation. The level of initiator and of chain transfer agent, ifpresent, is preferably controlled so that the number average molecularweight Mn of the polymer produced is not more than 10,000 and ispreferably in the range of 600 to 5,000, most preferably 1,000 to 3,000,in order to maintain a workable viscosity. However, it is possible toget a workable composition using a polymer with a molecular weight above1,000, albeit that relatively high levels of monomeric compounds and/orsolvent need to be added to achieve application viscosity. For example,the amount of free radical initiator used (by weight based on monomers)is generally at least 1%, preferably 2 to 10%, when no chain transferagent is used, or a level of 1 to 5% initiator can be used inconjunction with 1 to 10% chain transfer agent.

[0028] The coating composition according to the present invention alsocomprises a hardener or curing agent. The curing agent which is presentin the curable polymer composition in general can be any curing agentactive in crosslinking the functional groups present in the olefinicallyunsaturated polymer andlor in the reactive diluent under the intendedconditions of curing. The curing agent can for example bethiol-functional or amino-functional. Preferably, the curing agent is anamine chosen from the general classes of aliphatic amines, aliphaticamine adducts, polyamidoamines, cycloaliphatic amines and cycloaliphaticamine adducts, aromatic amines, Mannich bases, and ketimines, which eachmay be substituted wholly or in part with an aminosilane having thegeneral formula Y—Si—(O—X)₃, wherein Y is H(HNR)a and a is an integerfrom one to six, each R is a difunctional organic radical independentlyselected from the group consisting of aryl, alkyl, dialkylaryl,alkoxyalkyl, and cycloalkyl radicals, and R can vary within each Ymolecule. Each X may be the same or different, and is limited to alkyl,hydroxyalkyl, alkoxyalkyl, and hydroxyalkoxyalkyl groups containingfewer than about six carbon atoms.

[0029] Preferred aminosilanes are, for example: 3-aminoethyltriethoxysilane, 3-aminopropyl triethoxysilane, n-phenylaminopropyltrimethoxysilane, trimethoxysilylpropyl diethylene triamine,3-(3-aminophenoxy)propyl trimethoxysilane, aminoethyl aminomethylphenyltrimethoxysilane, 2-aminoethyl 3-aminopropyl, tris 2-ethylhexoxysilane,n-aminohexyl aminopropyl trimethoxysilane, and trisaminopropyltrimethoxy ethoxysilane, or mixtures thereof.

[0030] However, the curing agent can also contain a mercaptosilane, apolyamine, or polythiol.

[0031] In a preferred embodiment, the coating composition comprises from45 to 75% by weight of the polysiloxane, from 20 to 45% by weight of theglycidyl-functional acrylic polymer, and from 4 to 11% by weight of thehardener. Optimum results are found for a coating composition comprisingfrom 60 to 70% by weight of the polysiloxane, from 20 to 30% by weightof the glycidyl-functional acrylic polymer, and from 7 to 11% by weightof the hardener. The % by weight is calculated on the basis of theweight of the coating composition.

[0032] Optionally, the coating composition according to the presentinvention comprises a low-molecular weight alkoxysilane having thegeneral formula

[0033] wherein R3 is selected from the group consisting of alkyl andcycloalkyl groups containing up to six carbon atoms and aryl groupscontaining up to ten carbon atoms. R4 is independently selected from thegroup consisting of alkyl, hydroxyalkyl, alkoxyalkyl, andhydroxyalkoxyalkyl groups containing up to six carbon atoms. R5 isindependently selected from the group consisting of alkyl, alkoxy,hydroxyalkyl, alkoxyalkyl, and hydroxyalkoxyalkyl groups containing upto six carbon atoms. An example of a low-molecular weight alkoxysilaneaccording to the above formula that can be used in the coatingcomposition is dimethoxydiphenyl silane.

[0034] The coating compositions according to the invention may contain acompound which acts as a catalyst for Si—O—Si condensation. In general,the coatings are capable of curing under ambient temperature andhumidity conditions to a tack-free coating in 2 to 20 hours even withoutsuch a catalyst, but a catalyst may be preferred to give a faster cure.

[0035] One example of a catalyst for Si—O—Si condensation is analkoxytitanium compound, for example a titanium chelate compound such asa titanium bis(acetylacetonate) dialkoxide, e.g., titaniumbis(acetylacetonate) diisopropoxide, a titanium bis(acetoacetate)dialkoxide, e.g., titanium bis(ethylacetoacetate) diisopropoxide, or analkanolamine titanate, e.g., titanium bis(triethanolamine)diisopropoxide, or an alkoxytitanium compound which is not a chelatesuch as tetra(isopropyl) titanate or tetrabutyl titanate. Such titaniumcompounds containing alkoxy groups bonded to the titanium may not act ascatalysts alone, since the titanium alkoxide group is hydrolysable andthe catalyst may become bound to the cured silane or siloxane by Si—O—Tilinkages. The presence of such titanium moieties in the cured productmay be advantageous in giving even higher heat stability. The titaniumcompound can for example be used at 0.1 to 5% by weight of the binder.Corresponding alkoxide compounds of zirconium or aluminium are alsouseful as catalysts.

[0036] An alternative catalyst is a nitrate of a polyvalent metal ionsuch as calcium nitrate, magnesium nitrate, aluminium nitrate, zincnitrate, or strontium nitrate. Calcium nitrate has been suggested as acatalyst for the amine curing of epoxy resins, but it has never beensuggested for the curing of silane or siloxane materials. Surprisingly,we have found that calcium nitrate is an effective catalyst for thecuring by Si—O—Si condensation of a silane or siloxane containing atleast two alkoxy groups bonded to silicon by Si—O—C bonds, when thecomposition also includes an organic amine. The calcium nitrate ispreferably used in its tetrahydrate form but other hydrated forms can beused. The level of calcium nitrate catalyst required is generally notmore than 3% by weight of the binder, for example 0.05 to 3% by weight.Coatings cured using calcium nitrate catalyst are especially resistantto yellowing on exposure to sunlight.

[0037] Another example of a suitable catalyst is an organotin compound,for example a dialkyltin dicarboxylate such as dibutyltin dilaurate ordibutyltin diacetate. Such an organotin catalyst can for example be usedat 0.05 to 3% by weight of the binder of the coating composition.

[0038] Other compounds effective as catalysts in the coatingcompositions of the invention are organic salts, such as carboxylates,of bismuth, for example bismuth tris(neodecanoate). Organic salts and/orchelates of other metals such as zinc, aluminium, zirconium, tin,calcium, cobalt, or strontium, for example zirconium acetylacetonate,zinc acetate, zinc acetylacetonate, zinc octoate, stannous octoate,stannous oxalate, calcium acetylacetonate, calcium acetate, calcium2-ethylhexanoate, cobalt naphthenate, calcium dodecylbenzenesulphonate,or aluminium acetate, may also be effective as catalysts.

[0039] The coating compositions of the invention may contain one or morefurther ingredients. They may for example contain one or more pigments,for example titanium dioxide (white pigment), coloured pigments such asyellow or red iron oxide or a phthalocyanine pigment and/or one or morestrengthening pigments such as micaceous iron oxide or crystallinesilica and/or one or more anticorrosive pigments such as metallic zinc,zinc phosphate, wollastonite or a chromate, molybdate or phosphonateand/or a filler pigment such as barytes, talc or calcium carbonate. Thecomposition may contain a thickening agent such as fine-particle silica,bentonite clay, hydrogenated castor oil, or a polyamide wax. Thecomposition may also contain a plasticiser, pigment dispersant,stabiliser, flow aid, or thinning solvent.

[0040] The coating compositions of the invention generally cure atambient temperatures, for example 5 to 30° C., and are thus suitable forapplication to large structures where heat-curing is impractical. Thecoating compositions of the invention alternatively can be cured atelevated temperatures, for example from 30 to 50° C. up to 100 or 130°C., to speed up the curing. The hydrolysis of silicon-bonded alkoxygroups depends on the presence of moisture; in almost all climatesatmospheric moisture is sufficient but a controlled amount of moisturemay need to be added to the coating when curing at elevated temperatureor when curing in very low humidity (desert) locations. The water ispreferably packaged separate from any compound or polymer containingsilicon-bonded alkoxy groups.

[0041] The coating compositions of the invention in general can be usedas finish coatings and/or primer coatings. Coating compositionscontaining a relatively high proportion of polysiloxane have a highgloss which is retained remarkably well on weathering and UV exposure.They are particularly suitable for coating substrates which are exposedto the weather, e.g. sunlight, for long periods before recoating. Thehighest levels of gloss may be achieved if the coating compositionincludes an organic solvent (thinner) such as xylene, although use ofsolvent is not generally necessary in the coating compositions of theinvention, which can be 100% solids coatings having a very low measuredvolatile organic content. The coating composition may contain analcohol, e.g. ethanol or butanol, preferably packaged with thealkoxysilyl-functional component, to extend pot life and control initialspeed of curing. A finish coating according to the invention can beapplied over various primer coatings, for example inorganic zincsilicate or organic zinc-rich silicate primers and organic, e.g. epoxyresin, primers containing zinc metal, corrosion-inhibiting, metal flakeor barrier pigments. The coating composition of the invention hasparticularly good adhesion to inorganic zinc silicate coatings withoutneeding an intermediate tie coat or mist coat. A finish coatingcomposition of the invention can also be applied directly over aluminiumor zinc “metal spray” coatings, in which case it acts as a sealer aswell as a top coat, or over galvanised steel, stainless steel,aluminium, or plastics surfaces such as glass fibre reinforced polyesteror a polyester gel coat. The coating composition can for example be usedas a finish coating on buildings, steel structures, automobiles,aircraft and other vehicles, and general industrial machinery andfitments. The finish coating can be pigmented or it can be a clear(non-pigmented) coat, particularly on cars or yachts. The coatingcomposition can be applied directly to prepared carbon steel as aprimer/finish.

[0042] The coating composition of the invention alternatively can beused as a protective primer coating, particularly on steel surfaces, forexample bridges, pipelines, industrial plants or buildings, oil and gasinstallations, or ships. For this use it is generally pigmented withanticorrosive pigments. It may for example be pigmented with zinc dust;coatings according to the invention have a similar anticorrosiveperformance to known zinc silicate coatings but are less liable tomud-cracking and can be readily overcoated, particularly with apolysiloxane finish, for example a finish coat according to the presentinvention. Primer coating compositions according to the invention can beused as maintenance and repair coatings on less than perfect surfacessuch as aged blasted steel or “ginger” (steel which has been blasted andhas started to rust in small spots), hand-prepared weathered steel, andaged coatings.

[0043] As well as outstanding resistance to UV weathering, the coatingsproduced from the compositions of the invention have good flexibilityand adhesion to most surfaces and have higher heat resistance (up to150° C. and usually up to 200° C.) than most organic coatings.

[0044] The invention will be elucidated with reference to the followingexamples. These are intended to illustrate the invention but are not tobe construed as limiting in any manner the scope thereof.

[0045] In the examples, pbw has the meaning of parts by weight.

EXAMPLES Example 1

[0046] (Polymer Preparation)

[0047] An acrylic polymer was prepared in a reaction vessel equippedwith a mechanical stirrer, a nitrogen inlet tube, a temperaturecontroller, a reflux condenser, and inlet tubes for the addition ofreagents during the reaction. A polysiloxane (Dow Corning DC 3074) wascharged to the vessel and heated to 140° C. with stirring undernitrogen. A mixture of butyl acrylate, glycidyl methacrylate, methylmethacrylate, and an initiator (di-tert butyl peroxide=Trigonox B) wasadded over a period of 4 hours. After the addition was completed, thetemperature was maintained at 140° C. for 2 hours. Then the product wasallowed to cool before being discharged from the reaction vessel. Theviscosity of the obtained product was measured at 25° C. using aBrookfield 1000 CAP viscometer equipped with a no.6 cone. Details on theformulation and its properties are given in Table 1.

Example 2

[0048] (Polymer Preparation)

[0049] An acrylic polymer was prepared using the method of Example 1,with the reaction being carried out at 150° C. Details on theformulation and its properties are given in Table 1.

Examples 3-18

[0050] (Polymer Preparation)

[0051] Different acrylic polymers were prepared using the method ofExample 1. Details on the formulations and their properties are given inTable 1.

Example 19

[0052] (Polymer Preparation)

[0053] An acrylic polymer was prepared using the method of Example 1,with the reaction being carried out at 114° C. Trigonox 42S in 5 partsby weight of xylene was used as initiator. Details on the formulationand its properties are given in Table 1.

Example 20

[0054] (Polymer Preparation)

[0055] An acrylic polymer was prepared using the method of Example 1,with the reaction being carried out at 85° C. Trigonox 141 in 5 parts byweight of xylene was used as initiator. Details on the formulation andits properties are given in Table 1.

Example 21

[0056] (Coating Composition)

[0057] A coating composition was prepared using polymer 1 by mixingpolymer 1 and pigment (titanium dioxide) using a high-speed dispenser.Xylene was added to reduce the viscosity of the mixture below 10 Poise.A curing agent (3-aminopropyltriethoxysilane) and a catalyst (dibutyltindiacetate) were added and the mixture was stirred by hand before beingapplied to test panels. Details on the formulation of the coatingcomposition and its viscosity properties are given in Table 2.

Example 22

[0058] (Coating Composition)

[0059] A coating composition was prepared using polymer 2 by mixingpolymer 2 and titanium dioxide using a high-speed dispenser. Xylene wasadded to reduce the viscosity of the mixture below 10 Poise. A curingagent (3-aminopropyl-triethoxysilane) and a catalyst (bismuthneodecanoate) were added and the mixture was stirred by hand beforebeing applied to test panels. Details on the formulation of the coatingcomposition and its viscosity properties are given in Table 2. TABLE 1DC Visco Visco 3074¹ BA² GMA³ MMA⁴ Tri-B⁵ A⁶ B⁷ Example (pbw) (pbw)(pbw) (pbw) (pbw) (Poise) (Poise)  1 61 25  8 6 1.3 69 8  2 70 17 13 01.3 20.5  3 55 15 15 15  1.6 >100 64   4 72 10 12 7 1.0 67 6  5 50 25 155 1.5 >100 22   6 65 17 11 7 1.2 >100 11   7 61 16  8 15  1.5 >100 16  8 78 15  8 0 0.8 15 2  9 68 10  8 15  1.3 >100 10  10 64 25 11 0 1.2 466 11 78 10 12 0 0.7 18 2 12 55 20 15 10  1.6 >100 36  13 71 16  9 3 1.028 3 14 68 18 15 0 1.1 51 5 15 68 18 15 0 1.1 53 6 16 60 10 15 15 1.5 >100 54  17 78 15  8 0 0.8 15 2 18 55 22  8 15  1.7 >100 27  19 7017 13 0 1.0⁸ 16 20 70 17 13 0 1.0⁹ 32

Examples 23-38

[0060] (Coating Compositions)

[0061] Coating compositions were prepared according to the procedure ofExample 21, using polymers 3-18. Details on the formulation of thecoating compositions and their viscosity properties are given in Table2.

[0062] Some of the test panels were irradiated with UV-A or UV-Bradiation under accelerated test conditions. They showed a glossretention of about 90% after 200 days of UV-A irradiation. This is amajor improvement in comparison to state of the art protective coatingsbased on polysiloxane formulations.

[0063] The panels showed a gloss retention of about 40% after 200 daysof UV-B irradiation. This is also a major improvement in comparison tostate of the art protective coatings based on polysiloxane formulations,which show a gloss retention well below 10% upon UV-B irradiation forsuch a period of time. TABLE 2 Coating Polymer Polymer Pigment C.A.¹Cat.² xylene Vis- Example Example (pbw) (pbw) (pbw) (pbw) (pbw) co³ 21 160 30 3 0.2 11 4.7 22 2 67 33 6.6 0.1 0 23 3 54 27 7 0.3 19 4.0 24 4 6130 5 0.3 9 4.2 25 5 57 29 5 0.3 14 4.4 26 6 59 29 4 0.2 12 4.0 27 7 5829 3 0.2 13 5.2 28 8 63 32 3 0.2 5 4.4 29 9 59 30 3 0.2 11 4.3 30 10 6130 4 0.2 9 4.5 31 11 63 32 5 0.2 5 3.9 32 12 56 28 6 0.3 16 4.0 33 13 6231 3 0.2 7 4.2 34 14 61 30 6 0.3 9 3.3 35 15 59 29 3 0.2 12 4.8 36 16 6130 6 0.3 9 3.5 37 17 63 32 3 0.1 5 4.6 38 18 57 28 3 0.2 15 5.0

1. Ambient temperature curing coating composition comprising apolysiloxane having the formula

wherein each R1 is selected from the group consisting of alkyl, aryl,and alkoxy groups having up to six carbon atoms, reactive glycidoxygroups, and OSi(OR3)₃ groups, wherein each R3 independently has the samemeaning as R1, each R2 is selected from the group consisting of hydrogenand alkyl and aryl groups having up to six carbon atoms, and wherein nis selected so that the molecular weight of the polysiloxanes is in therange of from 500 to about 2,000, a glycidyl-functional acrylic polymer,a hardener.
 2. Coating composition according to claim 1 , wherein theglycidyl-functional acrylic polymer is obtained by polymerisation in thepolysiloxane.
 3. Coating composition according to claim 1 , wherein thepolysiloxane is an alkoxysilyl-functional polysiloxane.
 4. Coatingcomposition according to claim 1 , wherein the glycidyl-functionalacrylic polymer is obtained by polymerising a mixture comprisingglycidyl methacrylate and butyl acrylate.
 5. Coating compositionaccording to claim 4 , wherein the mixture further comprises methylmethacrylate.
 6. Coating composition according to claim 5 , wherein themixture comprises 15-75% by weight of glycidyl methacrylate, 0-60% byweight of methyl methacrylate, and 30-85% by weight of butyl acrylate.7. Coating composition according to claim 1 , wherein the compositioncomprises from 45 to 75% by weight of the polysiloxane, from 20 to 45%by weight of the glycidyl-functional acrylic polymer, and from 4 to 11%by weight of the hardener, with % by weight being calculated on thebasis of the weight of the coating composition.
 8. Coating compositionaccording to claim 7 , wherein the composition comprises from 60 to 70%by weight of the polysiloxane, from 20 to 30% by weight of theglycidyl-functional acrylic polymer, and from 7 to 11% by weight of thehardener, with % by weight being calculated on the basis of the weightof the coating composition.
 9. Use of a coating composition according toclaim 1 as a protective coating.
 10. Use of a coating compositionaccording to claim 1 for the coating at ambient temperature of largestructures such as ships, bridges, buildings, industrial plants, or oilrigs.